1. 1Ruđer Bošković Institute, Zagreb, Croatia
Generation of vacancy-related defects during focused swift-ion beam implantation of silicon
I.Capan1, M.Jakšić1, Ž. Pastuović1,2, Rainer Siegele2, David Cohen2
1Ruđer Bošković Institute, Zagreb, Croatia
2 Centre for Accelerator Science, IER, ANSTO, 1 New Illawarra Rd, Lucas heights NSW 2234, Australia

2. Silicon Detector Workshop
Introduction
Influence of high energies/high fluences of particles on silicon-based detectors;
Can heavier ions offer cost effective simulation of radiation damage produced in semiconductor detectors by p, n, e?
Ion beams  dense regions of vacancies and interstitials in bulk semiconductor  clustering;
Electrically active cluster-related damage in silicon:
Structure?
Capture kinetics?
Split, 8-10 October 2012
Silicon Detector Workshop

3. Silicon Detector Workshop
Introduction
RD’s in n-type CZ Si
V2(-/0) VO VO
V2(=/-) ? VV
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Silicon Detector Workshop

4. Silicon Detector Workshop
Introduction
Divacancy & ion mass effect
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Silicon Detector Workshop

5. Silicon Detector Workshop
Introduction
Models for interpretation of the DLTS observed mass effect:
(i) the lattice distortation and strain due to accumulated damage produced by heavy ions in the highly localized collision cascades can prevent, to a large extent, the electronic bond switching. The effect increases with ion mass because a density of elastic energy deposition, i.e. primary defect generation rate increases and causes larger distrortation and strain in the crystal lattice. Since the electronic bond switching is a thermally activated process, V2(=/-) peak is more influenced by the lattice strain than V2(-/0) peak (V2(=/-) defect has a low activation temperature of 115K ), PRB 55 (1997);
Split, 8-10 October 2012
Silicon Detector Workshop

6. Silicon Detector Workshop
Introduction
Models for interpretation of the DLTS observed mass effect:
(ii) suppression of the DLTS signal from shallow states is due to a local depletion of the carrier concentration in the dense defect cascade region which leads to incomplete occupation of the shallow states such as VO and V2(=/-) in heavy ion implanted n-Si, PRB 65 (2002);
(iii) additional electrically active defects, e.g., vacancy-clusters (Vx, x>2) that artificially enhance the V2(-/0) signal, J. Appl. Phys. 93 (2003);
Split, 8-10 October 2012
Silicon Detector Workshop

7. Silicon Detector Workshop
Experiment
The materials used in our experiment were phosphorus-doped Czohralski-grown (CZ) silicon wafers with initial resistivities of (1–2)  cm.
The Au/n-Si Schottky diodes were formed by thermal evaporation of gold on etched Si surface
The samples (D=1mm) were uniformly irradiated at RT with scanning focused 8.3 MeV Si3+ ion micro-beam (I=5 F=4x1012 ions/cm-2s-1) up to dose of cm-2.
Deep traps were characterized with depth resolving deep level transient spectroscopy (DLTS).
Split, 8-10 October 2012
Silicon Detector Workshop

8. Silicon Detector Workshop
Results  CV
Depth profile
DLTS scan
Averaged energy loss profiles of 8.3 MeV Si ions implanted in 100nm Au/n-Si Schottky diode (TRIM) w threshold for dense vacancy regime (PRB79)
Split, 8-10 October 2012
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9. Silicon Detector Workshop
Results  DLTS
Activation energy ?
VO VV VP
0.17
0.23 X
0.42
0.45
Low-doped material!
Is it a point-like
defect?
Split, 8-10 October 2012
Silicon Detector Workshop

10. Silicon Detector Workshop
Results  DLTS
Capture kinetics
Point-like defect kinetics!
PRB
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11. Results ? Two DLTS spectra (@ -1 – -0.2 V & @ -5 – -3 V) combined!
Defect depth profiling with DLTS ?
VV X X2
Interstitial-rich region
0.42
0.53
0.78
Vacancy-
rich region
Two new deep defect states from
interstitial-rich region emerge!
Two DLTS spectra -1 – -0.2 V -5 – -3 V) combined!
Split, 8-10 October 2012
Silicon Detector Workshop

12. Silicon Detector Workshop
Results  Laplace DLTS
LDLTS measured at 225K, i.e. the activation energy of VV (-/0) ~0.4 eV for:
Vacancy-rich region (-2, -1 V)
Interstitial-rich region (-5, -2.8 V)
Si : Si
T=225K
(Ec-0.4 eV)
LDLTS spectra from as implanted and annealed (180C 40min) sample measured at 225K for:
Vacancy-rich region (-2, -1 V)
Interstitial-rich region (-5, -2.8 V)
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13. Silicon Detector Workshop
Conclusions
VO and V2(=/-) completely suppressed
0.40 eV  vacancy-related defect
0.40 eV  cluster-related defect
And the model is ...
Split, 8-10 October 2012
Silicon Detector Workshop

14. Silicon Detector Workshop
TODO
Scanning capaictance microscopy (SCM)
Split, 8-10 October 2012
Silicon Detector Workshop